1. Field of the Invention
The present invention relates to an oxide magnetic material, particularly an M type ferrite magnet material containing R and Co.
2. Description of the Related Art
Generally, as an oxide permanent magnet material, magnetoplumbite type (M type) Sr ferrite or Ba ferrite of a hexagonal system is mainly used. These M type ferrites have been used as sintered magnets and bonded magnets, because the ferrites are relatively inexpensive and have high magnetic properties, and the ferrites are utilized, for example, in motors equipped in home electronics, cars, etc.
In recent years, electronic parts have been increasingly demanded to be downsized and exhibit high performance and, accordingly, a ferrite sintered magnet have also been strongly demanded to be downsized and exhibit high performance. For example, a ferrite sintered magnet with a high residual magnetic flux density and a high coercive force which cannot been attained by conventional M type ferrite sintered magnets is proposed in Japanese Patent Laid-Open No. 11-154604 (Patent Document 1). This ferrite sintered magnet contains Sr, La and Co at least, and has a hexagonal M type ferrite as a main component. Another hexagonal M type ferrite containing Sr, Pr and Co, or Sr, Nd and Co is disclosed in Japanese Patent Laid-Open No. 11-97226 (Patent Document 2) and Japanese Patent Laid-Open No. 11-195516 (Patent Document 3).
[Patent Document 1]
Japanese Patent Laid-Open No. 11-154604
[Patent Document 2]
Japanese Patent Laid-Open No. 11-97226
[Patent Document 3]
Japanese Patent Laid-Open No. 11-195516
However, these ferrite magnets have still been demanded to have improved coercive force and saturation magnetization. In addition, although these ferrite magnets have improved coercive force (HcJ) and residual magnetic flux density (Br) by incorporating Co therein, ferrite magnets are more expensive than before, since Co is expensive.
Accordingly, an object of the present invention is to provide a technology effective for improving the residual magnetic flux density (Br) and/or coercive force (HcJ) of a ferrite sintered magnet without increasing the content of Co.